![(3) Intramembranous Ossification
(3) Intramembranous Ossification
[~Begins Week 8]
• Cells produce fibrous membranes surrounding cartilage.
• Ossification Center forms within fibrous membrane.
• Osteoid (Nutrient + Osteoblast Mixture) secreted from
membrane.
• Osteoblasts develop into Osteocytes.
• Osteoid mineralizes around blood vessels, forming spongy
bone trabeculae.
• Remaining external Mesenchymal Cells form periosteum.
• Outer trabeculae lament and form thicker compact bone.
• Cranial Bones + Clavicles formed.](https://image.slidesharecdn.com/anatunit4bonegrowthanddevelopmentnotes-250129134843-00cca1f7/85/ANAT_unit-4_bone-growth-and-development-notes-ppt-5-320.jpg)
![(4) Endochondral Ossification
(4) Endochondral Ossification
[~Begins Week 10-12]
• Ossification Center forms within cartilage.
• Blood Vessels infiltrate, allowing for periosteum formation.
• Bone Collar forms around diaphysis of cartilage model.
• Osteoblasts within the Periosteum secrete osteoid, encasing
cartilage.
• Ossification Center calcifies, cartilage cells enlarge and die.
• Inner cavity invaded by periosteal bud (blood vessels, nerves,
osteoblasts).
• Osteoblasts surround dead cartilage cells, spongy bone trabeculae
formed.
• Innermost trabeculae devoured by osteoclasts, medullary cavity
formed.
• Outer trabeculae lament and form compact bone.](https://image.slidesharecdn.com/anatunit4bonegrowthanddevelopmentnotes-250129134843-00cca1f7/85/ANAT_unit-4_bone-growth-and-development-notes-ppt-8-320.jpg)
![(5) Endochondral Ossification:
(5) Endochondral Ossification:
The Epiphyses
The Epiphyses
[~Begins Week 27-29]
• Center (both inner and outer) of bone model
continues to ossify.
• Ends remain as cartilage, continue to undergo
mitosis Elongation.
• Ossification was “chasing” Cartilage
Formation to the ends of the bone.
• Epiphyses ossify…. Cartilage remains on
outer surface of epiphyses and at Epiphyseal
Plate.](https://image.slidesharecdn.com/anatunit4bonegrowthanddevelopmentnotes-250129134843-00cca1f7/85/ANAT_unit-4_bone-growth-and-development-notes-ppt-10-320.jpg)
ANAT_unit 4_bone growth and development notes.ppt
- 1. Bone Growth & Development”
- 2. Know This First!! Know This First!! • Osteo = Bone • Intra = Between • Perio = Outer • Endo = Inner • -blast, -cyte, -clast = types of cells • Mesenchymal Cells = Stem Cells for bone, cartilage, lymphatic structures and circulatory structures.
- 3. (1) Bone Development (1) Bone Development • Ossification = Bone Formation. • Part 1: Prenatal Formation of Bony Skeleton • Part 2: Postnatal Growth
- 4. (2) (2) Prenatal Formation of Prenatal Formation of Bony Skeleton Bony Skeleton • Bone Tissue will replace Cartilage Tissue • Initial Cartilage Tissue is resilient and flexible, allowing for increased mitosis. • THE STEPS: – Intramembranous Ossification: – Endochondral Ossification:
- 5. (3) Intramembranous Ossification (3) Intramembranous Ossification [~Begins Week 8] • Cells produce fibrous membranes surrounding cartilage. • Ossification Center forms within fibrous membrane. • Osteoid (Nutrient + Osteoblast Mixture) secreted from membrane. • Osteoblasts develop into Osteocytes. • Osteoid mineralizes around blood vessels, forming spongy bone trabeculae. • Remaining external Mesenchymal Cells form periosteum. • Outer trabeculae lament and form thicker compact bone. • Cranial Bones + Clavicles formed.
- 8. (4) Endochondral Ossification (4) Endochondral Ossification [~Begins Week 10-12] • Ossification Center forms within cartilage. • Blood Vessels infiltrate, allowing for periosteum formation. • Bone Collar forms around diaphysis of cartilage model. • Osteoblasts within the Periosteum secrete osteoid, encasing cartilage. • Ossification Center calcifies, cartilage cells enlarge and die. • Inner cavity invaded by periosteal bud (blood vessels, nerves, osteoblasts). • Osteoblasts surround dead cartilage cells, spongy bone trabeculae formed. • Innermost trabeculae devoured by osteoclasts, medullary cavity formed. • Outer trabeculae lament and form compact bone.
- 10. (5) Endochondral Ossification: (5) Endochondral Ossification: The Epiphyses The Epiphyses [~Begins Week 27-29] • Center (both inner and outer) of bone model continues to ossify. • Ends remain as cartilage, continue to undergo mitosis Elongation. • Ossification was “chasing” Cartilage Formation to the ends of the bone. • Epiphyses ossify…. Cartilage remains on outer surface of epiphyses and at Epiphyseal Plate.
- 15. (6) Postnatal Bone Growth (6) Postnatal Bone Growth • Long bones lengthen from the center ends. – Cartilage Cells w/in Epiphyseal Plate continue to divide = Growth + Lengthening. – Epiphyseal Cartilage Cells replaced by osteoblasts (the chase continues). – Eventually the “Plate” is replaced by bone. • All bones become thicker. – Periosteum continues to secrete osteoid on top of existing bone. – Osteoclasts on inside devour some bone. – Increased bone deposition, Decreased bone removal. – Thickness can increase due to increased bone stress! • Some facial bones continue to grow… past adolescence.
- 16. (7) Hormone Regulation (7) Hormone Regulation • During Infancy & Childhood: – Growth Hormone stimulates epiphyseal growth – Growth Hormone released by pituitary gland, but controlled by thyroid hormones. • During Puberty: – Testosterone and Estrogen are released slowly, in increasing amounts • Initially promotes growth spurt and masculinization / feminization • Later induce epiphyseal closure, ending growth